Insulation-crushing terminal assembly



A g- 14, 1962 D. E. CHENEY 3,049,691

INSULATION-CRUSHING TERMINAL ASSEMBLY Filed March 20, 1959 jrzdrziar.

United States Patent Ofifice 3,049,691 Patented Aug. 14, 1962 3 049 691INsULAnoN-cnUsHnscrERanNAL ASSEMBLY Donald E. Cheney, Wheaten, 111.,assignor to Reliable Electric Company, Franklin Park, 111., an Illinoiscom- Pally Filed Mar. 20, 1959, Ser. No. 800,882 Claims. (Cl. 33995)This invention relates to an insulationcrushing terminal for aplastic-insulated conductor, and more particuarly to a terminal whereinpressure is applied to remove the insulation from the conductor at theterminal.

Prior terminals have been devised which rely on pressure to crush awayand remove plastic insulation at the terminal. Such terminals, however,provide no control over the amount of pressure applied, with the resultthat there often is excess pressure. This excess pressure unduly deformsthe conductor, i.e. flattens it out, with consequent loss of mechanicalstrength. In fact, conductors often are broken in two in connecting themto such terminals. If not broken initially, they usually are weakened sobreaking occurs subsequently.

One object of the invention, therefore, is to provide a terminal forplastic-insulated conductors wherein pressure is employed to crush awayor remove the insulation but wherein means are provided for limiting theamount of pressure so that no significant conductor deformation occurs.

Another object of the invention is to provide such a terminal whichlends itself to use in various types of terminal devices, such asterminal attachments, terminal blocks, binding posts, etc.

Still another object of the invention is to provide such a termnialwhich is inexpensive to construct and which is highly efiective in use.

Other objects, advantages and details of the invention will becomeapparent as the description proceeds, reference being had to theaccompanying drawing wherein one embodiment of the invention is shown.It will be understood that the description and drawing are illustrativeonly and that the scope of the invention is to be measured by theappended claims.

In the drawings:

FIG. 1 is a fragmentary elevational view, partly in section, of aterminal block showing a portion of a terminal embodying the invention;

FIG. 2 is a top view of the terminal portion shown in FIG. 1, -a dottedline conductor shown applied to the terminal portion;

FIG. 3 is a fragmentary sectional view of a terminal block showing acomplete terminal embodying the invention, and

FIG. 4 is a fragmentary elevational view, partly in section, showing theterminal of FIG. 3 in operative engag ment with a plastic-insulatedconductor.

Before referring to the drawing in detail, a terminal embodying thepresent invention comprises a first member and a second memberrelatively movable toward each other. The opposing surfaces of thesemembers are generally flat and parallel to each other. The opposingsurface of one of the members has at least one protuberance, the top ofwhich lies in a plane spaced from the surface by a distance slightlyless than the diameter of a conductor, exclusive of insulation, to beused with the terminal. Finally, means are provided for forcing saidmembers toward each other with a plastic-insulated conductortherebetween until the second member engages the top of theprotuberance.

When the members are thus engaged, the force applied to the conductor islarge enough to crush away and remove the insulation from the conductorat the terminal and small enough to avoid significant conductordeformation and consequent loss of mechanical strength.

The protuberances, if more than one is employed, also perform theincidental function of confining the conductor and preventing it fromworking its way out from between the two members of the terminal.

Referring now to the drawing, the invention is shown embodied in aterminal of the binding post type mounted in a terminal block. It willbe understood, however, that the invention may be embodied in variousother types of terminal devices.

The numeral 5 designates a fragmentary portion of the exterior shell ofa terminal block. The interior of shell 5 contains suitable fillermaterial 6.

Referring particularly to FIGS. 3 and 4, the terminal of the inventionin its broadest aspect includes a first member 19 having a generallyflat surface 11. It also includes a second member 12 having a generallyflat surface 13. Members 10 and 12 are arranged so they are relativelymovable toward each other, with the generally flat surfaces 11 and 13opposing each other and in generally parallel relation.

Opposing surface 11 of first member 10 is provided with at least oneunyielding protuberance 15. As best shown in FIG. 2, four suchprotuberances 15 are employed in the illustrated embodiment. Theseprotuberances are so dimensioned that the tops thereof lie in and definea plane which is generally parallel to and spaced from surface 11 ofmember 19. As here shown, protuberances 15 are located in quadraturerelation on surface 11 of member 10. The protuberances provide apositive stop means limiting the possible proximity of the opposingsurfaces of the relatively movable members 10 and 12.

The numeral 20 designates a plastic-insulated conductor of the typecommonly used in the communications field at the present time. materialused for insulation on conductors of this type is polyethylene orpolyvinyl chloride. Such insulation material, while providingsatisfactory insulation, has the characteristic of readily being crushedaway from the conductor in response to the application of moderatepressure. This characteristic, of course, is taken advantage of interminals of this character to avoid the time con-. suming step ofphysically removing the insulation from the conductor before connectingthe conductor to the terminal. In the drawings the insulation isdesignated 21 and the metallic conductor itself is designated 22.

Means are provided for forcing members 10 and 12 toward each other andinto engaging relation whereby surface 13 of member 12 engages and ispositioned by the tops of protuberances 15 which act as a stop means.This final relationship is shown in FIG. 4.

In the form of the invention shown, the means for forcing the tworelatively movable members 10 and 12 together comprises a threaded stemmember 25 and a nut member 26. As shown, relatively movable member 10 isassociated with and has a fixed relation with threaded stem member 25,and relatively movable member 12, in the form of a washer, loosely isreceived on stem member 25. Nut member 26 serves to force movable member12 into engagement with the tops of protuberances 15, as best shown inFIG. 4.

As previously mentioned, the distance between surface 11 of member 10and the plane of the tops of protuberances 15 is slightly less than thediameter of metallic conductor 22. This relationship results in a slightdeformation of conductor 22, but such deformation is insignificant sofar as the mechanical strength of the conductor is concerned. Theresulting modest deformation is of proper amount to insure that thedeforming force is adequate mechanically to hold conductor 22 in theterminal. This force, however, is more than adequate to By way ofexample, plasticcrush away and remove insulation 21 from conductor 22 inthe regions thereof in engagement with members 11) and 12, thusproviding requisite electrical connection Without requirin g manualstripping.

Portion 30 of the illustrated terminal simply serves to anchor theterminal properly in the terminal block.

It will be seen that a terminal embodying the invention is efiective toapply a highly controlled pressure to a plastic-insulated conductorconnected to the terminal. This pressure is great enough to crush awayand remove the plastic insulation from the conductor at the terminal andto mechanically hold the conductor in place, and it is small enough toavoid significant conductor deformation and consequent loss ofmechanical strength.

From the above description it is thought that the construction andadvantages of the invention will be readily apparent to those skilled inthe art. Various changes in detail may be made without departing fromthe spirit or losing the advantages of the invention.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. An insulation-crushing terminal assembly comprising aplastic-insulated conductor, a first member and a second memberrelatively movable toward each other, the opposing surfaces of saidmembers being generally flat and parallel to each other, a plurality ofspaced unyielding protuberances on the said opposing surface of saidfirst member, the tops of said protuberances lying in and defining aplane spaced from said surface by a distance slightly less than thediameter of said conductor exclusive of insulation, and means forcingsaid members toward each other with said plastic insulated conductortherebetween until said second member engages the tops of saidprotuberances whereby the force applied to said conductor is largeenough to crush the insulation from the conductor to establishelectrical connection and small enough to avoid significant conductordeformation and consequent loss of mechanical strength.

2. An insulation-crushing terminal assembly comprising aplastic-insulated conductor, a first member and a second memberrelatively movable toward each other, the opposing surfaces of saidmembers being generally flat and parallel to each other, at least oneunyielding protuberance on the said opposing surface of one of saidmembers, the height of said protuberance above said 3 surface slightlyless than the diameter of said conductor exclusive of insulation, andmeans forcing said members toward each other with said-plasticinsulatedconductor therebetween until the top of the protuberance on said onemember engages the opposing surface of the other member whereby theforce applied to said conductor is large enough to crush the insulationfrom the conductor -to establish electrical connection and small enoughto avoid significant conductor deformation and consequent loss ofmechanical strength.

3. The combination of claim 2 wherein said opposing surface of said onemember has four spaced protuberances of equal height located inquadrature relation.

4. The combination of claim 2 wherein said forcing means comprises athreaded stem member and an associated nut member, and wherein one ofthe relatively movable members has a fixed relation with said sternmember and the other relatively movable member is a Washer on said stemmember between said nut member and said one movable member.

5. An insulation-crushing terminal assembly comprising aplastic-insulated conductor, a first member and a second memberrelatively movable toward each other, the opposing surfaces of saidmembers being generally fiat and parallel :toeach other, positive stopmeans on one of said members engageable with the other of said memberslimiting proximity of the relatively movable members at a spacingslightly less than the diameter of said conductor exclusive ofinsulation, and means forcing said members toward each other with saidplastic-insulated conductor therebetween until said positive stop meansbecomes effective whereby the force applied to said conductor is largeenough to crush the insulation from the conductor to establishelectrical connection and small enough to avoid significant conductordeformation and consequent loss of mechanical strength.

References Cited in the file of this patent UNITED STATES PATENTS1,206,376 Randall Nov. 28, 1916 1,867,918 Lofgren July 19, 19322,137,840 Hayes Nov. 22, 1938 2,558,851 Jacobi July 3, 1951 2,724,809Bunch Nov. 22, 1955

